It is known in the art to add various materials to animal feeds to achieve a number of purposes. One such purpose is set forth in applicant's above-identified parent application wherein natamycin is added to conventional animal feeds as an antifungal agent.
Numerous additives have been proposed for animal feeds as growth promoting agents. Antibiotics in particular have been proposed as growth promoting additives. For example, Coates et al., "J. Sci. Food Agric.", 3, pp. 43-48, January 1952, suggest procaine penicillin as an agent of this type. Coates et al. also discuss similar effects of streptomycin, sulphasuccidine, sulphaquinoxaline, 4-hydroxy-3-nitrophenylarsonic acid, aureomycin, terramycin, and polymyxin, disclosed in work by other authors. Groschke et al., "Research Notes", pp. 616-618 (1950), discuss chick growth effects of vitamin B.sub.12, stertomycin, and aureomycin. In "J. Sci. Food Agric.", 3, pp. 49-53, February 1952 Cuthbertson discloses the value of vitamin B.sub.12, and antibiotic supplements such as penicillin, as chick food additives. In an abstract by Fountaine et al., "Journal of Animal Science", Vol. 9, pp 646-647, February 1950, the use of aureomycin as a growth supplement for calves is discussed. Further, Underkofler and Hickey, in "Industrial Fermentations" pp. 342-343 (1954), discuss the use of antibiotics such as streptomycin as growth promoters. All of the antibiotics disclosed in these publications are antibacterial antibiotics and are believed to be useful because the eliminate harmful bacteria or reduce the number of microorganisms in the intestinal tract, as discussed by Underkofler and Hickey.
As disclosed in U.S. Pat. No. 2,903,356, to Lampen et al. a growth promoting supplement comprising a combination of an antibacterial antibiotic with a member of the class consisting of nystatin and amphotericin is useful. This composition was said to accelerate the growth of animals by administration of feedstuffs containing the growth promoting supplement. In this patent there is discussed the need to include a sufficient amount of a factor identified as an animal protein factor in order to promote maximum growth. Thus, as defined in this patent, the expression "growth promoting agent" is an agent which will achieve an acceleration in the growth rate of animals superior to that obtainable with a normal diet.
Nystatin is a member of the class of antibiotics known as polyene antibiotics. These antibiotics have activity against yeasts and fungi, but have no significant activity against bacteria.
The present invention is also concerned with animal feed additives. However, in the present invention, a feed efficiency agent is incorporated into the animal food, said feed efficiency agent being effective to cause an animal to grow to its normal weight while requiring less feed than normal. Thus, the additive of the present invention is to be distinguished from growth promotion agents as discussed, for example, in U.S. Pat. No. 2,903,356.